LAB 4 : SOURCES OF CONTAMINATION AND INFECTIONS

INTRODUCTION

Contamination is the state of being impure or unfit for use due to the introduction of unwholesome or undesirable elements, contaminated by insects, rodents, chemicals, microbes, or other foreign particles. In food chemistry and medicinal chemistry, contamination is used to describe harmful intrusions, such as the presence of toxins or pathogens in food orpharmaceutical drugs. In forensic science, a contaminant can be fingerprints, hair, skin or DNA from first responders or from sources not related to the ongoing investigation, such as family members or friends of the victim who are not suspects. In the biological sciences, accidental introduction of contaminant can seriously distort the results of experiments where small samples are used. In cases where the contaminant is a living microorganism, it can often multiply and take over the experiment, especially cultures, and render them useless.

Do you ever wonder why you got sick? Chances are that you most likely got sick from an airborne pathogen. In other words, the germ or irritant floated from one person to another. Airborne microorganisms are usually carried on dust particles , some of them may also be carried by direct air currents. Airborne particles are a major cause of respiratory ailments of humans, causing allergies, asthma, and pathogenic infections of the respiratory tract. During a sneeze, millions of tiny droplets of water and mucus are expelled at about 200 miles per hour (100 metres per second). The droplets initially are about 10-100 micrometres diameter, but they dry rapidly to droplet nuclei of 1-4 micrometres, containing virus particles or bacteria.

Every human is colonized by billions of microorganisms. Microorganisms may live as individuals or cluster together in communities. They live in the water we drink, the food we eat, and the air we breathe. The number of normal bacterial cells that live on the body is in the region of 100 million. This number is 10 times greater than the 10 million cells that make up the human body.

Bacteria  could be divided into two categories, namely resident or transient. The resident flora consists of microorganisms residing under the superficial cells of the stratum corneum and can also be found on the surface of the skin. Resident flora has two main protective function microbial antagonism and the competition for nutrients in the ecosystem. In general, resident flora is less likely to be associated with infections, but may cause infections in sterile body cavities, the eyes, or on non-intact skin.

Transient flora (transient microbiota), which colonizes the superficial layers of the skin, is more amenable to removal by routine hand hygiene. Transient microorganisms do not usually multiply on the skin, but they survive and sporadically multiply on skin surface.The transmissibility of transient flora depends on the species present, the number of microorganisms on the surface, and the skin moisture.

OBJECTIVE

• To determine the microorganisms in the air and from healthy humans.
• To practice the correct procedure and steps for the pour plating technique.
• To compare the differences between self-made and commercial Nutrient Broth Agar.

MATERIAL AND REAGENTS

• Molten nutrient agar
• Sterile water
• Sterile petri dishes
• Sterile clinical swab
• Pipette and tips

PROCEDURE

( Refer to lab manual )

RESULTS AND OBSERVATIONS

Figure 1 : Sample from air , top : commercial ; bottom : self-made

Figure 2 : Sample from hand , top : commercial ; bottom : self-made

Figure 3 : Sample from ear , top : commercial ; bottom : self-made

Figure 4 : Sample from normal breathing , top : commercial ; bottom : self-made

Figure 5 : Sample from violent coughing , top : commercial ; bottom : self-made

Collection of colonies	Self-made nutrient agar	Commercial nutrient agar
Air	Form : Circular Elevation : Convex Size : Small Surface : Smooth Texture : Moist Colour : Pale yellow Margin : Entire	Shape : Circular Elevation : Convex Size : Small Surface : Smooth Texture : Moist Colour : White Margin : Entire
Hands	Form : Circular , Irregular Elevation : Raised Size : Small Surface : Smooth and shiny Texture : Slightly moist Colour : White Margin : Entire and endulate	Form : Circular , Irregular Elevation : Flat Size : Small , some are large Surface : Smooth and shiny Texture : Moist Colour : Yellow Margin : Entire , Endulate
Ear	Form : Circular , Irregular Elevation : Convex , Raised Size : Small and some are large Surface : Smooth and shiny Texture : Moist Colour : Yellow and white Margin : Entire	Form : Circular , Irregular Elevation : Raised , Convex Size : Small and some are large Surface : Smooth and shiny Texture : Moist Colour : Yellow and white Margin : Entire
Normal breathing	Form : Circular Elevation : Raised Size : Small Surface : Smooth and shiny Texture : Dry Colour : Yellow Margin : Entire	Form : Circular Elevation : Raised Size : Small Surface : Smooth and shiny Texture : Dry Colour : Pink Margin : Entire
Violent coughing	Form : Circular Elevation : Raised Size : Small Surface : Smooth and shiny Texture : Dry Colour : Pink Margin : Entire	Form : Circular Elevation : Umbonate Size : Small Surface : Smooth and shiny Texture : Dry Colour : Yellow Margin : Entire , Endulate

DISCUSSION

Figure 6 : Colony morphology chart 

Bacterial populations grow extremely fast under the desired nutrients and environmental conditions. Different types of bacteria will produce colonies that are distinctive in appearance in terms of colours, shapes and sizes. In this experiment, all the aspects including form, elevation, size, surface, texture, colour and margin are studied. The differences between self-made nutrient agar and commercial nutrient agar are compared based on the morphology observed.

What we observed from the media contaminated by air is that in overall, the colonies are the fewest compared to the other media prepared. For the self-made agar media, there are a few small and circular colonies with different sizes. The colonies formed are pale yellow in colour. As for the commercial nutrient agar, only one circular colony is observed and it is white in colour.

As for the media contaminated by hand, the colonies formed are much more than what we observed by air. From here, we may assume that our hands actually contains more microorganisms or microbes than the air because we are always in contact with lots of stuff in our daily life. For the self-made agar media, it is less moist than the commercial agar media. Both of the media contains circular and some irregular bacterial colonies.

For ear contamination, the sample was taken by an ear pick. The sample is collected from the outer part of our ear and is spread on the culture by using the streaking plate technique. For the commercial nutrient agar media, it contains more colonies than the self-made nutrient agar. For the commercial nutrient agar media , it contains colonies which are mostly circular and yellow coloured colonies throughout the whole plate, being concentrated in the centre of the plate. On the other hand, for the self-made nutrient agar media, it also contains small, circular and yellow coloured colonies but are more concentrated on the sides of the plate.

For violent coughing, the colonies that could be observed is also a little, especially for the self-made nutrient agar media. Only spores like size of circular microbes can be observed under a dry texture. As for the commercial nutrient agar, a few larger sizes of circular colonies can be seen and they are yellow in colour.

The colonies observed for normal breathing is also less, there are only a few spots of colonies formed. For the self-made nutrient agar media, a yellow circular colony can be seen under a dry texture. As for the commercial nutrient agar media , a pink circular colony is seen.

CONCLUSION

In conclusion, it is important to learn the correct steps for the pour plating technique and streaking plate technique to isolate the colonies. As we can see, there are no obvious or significant differences between the colonies that grow in a self-made nutrient agar media and a commercial nutrient agar media. We also learn that it is actually important to learn about colony morphology because this is one of the ways to actually help us differentiate between different colonies and helps us in identification.

REFERENCE

1 . Obtained from https://en.wikipedia.org/wiki/Contamination on 1 November 2015.

2 . Obtained from http://www.ncbi.nlm.nih.gov/books/NBK144001/ on 1 November 2015.